Copper frequently used for wirings in semiconductor devices is difficult to process by an etching method. Therefore, copper wirings are often formed by embedding copper in an insulating film using a damascene method. However, as the semiconductor devices have been increasingly downscaled, embedment of copper has become more difficult. Furthermore, the resistivity of copper wirings greatly increases due to thinning. To compensate an increase in the resistivity, it is conceivable to increase the height (thickness) of the copper wirings. In this case, however, the aspect ratio increases and thus embedment of copper becomes more difficult.
On the other hand, tungsten does not require application of the damascene method and can be processed by an etching technology. Furthermore, tungsten has a higher embeddability than copper. Therefore, tungsten wirings are considered as a substitute for copper wirings. However, in wider wirings, tungsten generally has a higher resistivity than copper. Therefore, when tungsten wirings are used in a semiconductor memory that has a memory area having a small wiring width and a peripheral area having a large wiring width, or the like, the wiring resistance becomes high in the peripheral area while fine wirings can be formed in the memory area.